1. Field
This invention relates to a method and apparatus useful in the differential diagnosis of multiple sclerosis.
2. State Of the Art
Multiple sclerosis ("MS") is a disease which usually presents itself in the form of recurrent attacks of focal or multifocal neurologic dysfunction. Its symptoms are multi-faceted and indefinite and include impaired vision, nystagmus, an inability to speak clearly, a decreased perception of vibration and position sense, intention tremor, muscular incoordination, limb weakness or paralysis, spasticity, and bladder problems. Harrison's Principles of Internal Medicine, p. 1995-2000 (11th ed. 1987). Unfortunately, no effective treatment of MS is known.
In order to establish a definite diagnosis of MS, at least two episodes of neurological deficit must occur along with objective clinical signs of lesions at more than one site within the central nervous system. One problem with such a diagnostic method is that a period of ten to twenty years may pass between episodes of neurological deficit. Id.
Another problem is that the symptoms of MS are so indefinite that it may be confused with several other conditions. It is therefore important during the differential diagnosis of the patient to exclude conditions having similar symptoms which can be effectively treated. For example a patient may be suffering from side-effects of various prescription drugs (e.g. phenytoin which can cause nystagmus, vertigo and muscle weakness), pernicious anemia, or various infections. Usually such conditions can be effectively treated.
A need therefore exists for a relatively simple device useful in the determination of whether or not someone might be suffering from MS.